CRTAC1: ProductsCRTAC1 (cartilage acidic protein 1; also CEP-68) is a 95-105 kDa member of a novel family of EGF domain-containing proteins. It is secreted by articular chondrocytes and may play a role in either cartilage matrix organization, or cell-matrix adhesion. Mature human CRTAC1 is 634 amino acids (aa) in length. It contains four FG-GAP (PheGly-GlyAlaPro) domains (aa 46-437) and one EGF-like motif (aa 559-605). Multiple splice forms exist. There are two alternate start sites at Met9 and Met211 that may be accompanied by a 39 aa substitution for the C-terminal 55 aa, or an 84 aa substitution for aa 545-661. Over aa 28-661, human CRTAC1 shares 91% aa identity with mouse CRTAC1. This form in mouse, however, is more equivalent to the human isoform that shows a C-terminal 39 aa substitution. In this case, there is 95% aa identity between mouse and human.